block/dmg.c - qemu - Git at Google

 /*
  * QEMU Block driver for DMG images
  *
  * Copyright (c) 2004 Johannes E. Schindelin
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
 #include "qemu-common.h"
 #include "block/block_int.h"
 #include "qemu/bswap.h"
 #include "qemu/module.h"
 #include <zlib.h>

 enum {
     /* Limit chunk sizes to prevent unreasonable amounts of memory being used
      * or truncating when converting to 32-bit types
      */
     DMG_LENGTHS_MAX = 64 * 1024 * 1024, /* 64 MB */
     DMG_SECTORCOUNTS_MAX = DMG_LENGTHS_MAX / 512,
 };

 typedef struct BDRVDMGState {
     CoMutex lock;
     /* each chunk contains a certain number of sectors,
      * offsets[i] is the offset in the .dmg file,
      * lengths[i] is the length of the compressed chunk,
      * sectors[i] is the sector beginning at offsets[i],
      * sectorcounts[i] is the number of sectors in that chunk,
      * the sectors array is ordered
      * 0<=i<n_chunks */

     uint32_t n_chunks;
     uint32_t* types;
     uint64_t* offsets;
     uint64_t* lengths;
     uint64_t* sectors;
     uint64_t* sectorcounts;
     uint32_t current_chunk;
     uint8_t *compressed_chunk;
     uint8_t *uncompressed_chunk;
     z_stream zstream;
 } BDRVDMGState;

 static int dmg_probe(const uint8_t *buf, int buf_size, const char *filename)
 {
     int len;

     if (!filename) {
         return 0;
     }

     len = strlen(filename);
     if (len > 4 && !strcmp(filename + len - 4, ".dmg")) {
         return 2;
     }
     return 0;
 }

 static int read_uint64(BlockDriverState *bs, int64_t offset, uint64_t *result)
 {
     uint64_t buffer;
     int ret;

     ret = bdrv_pread(bs->file, offset, &buffer, 8);
     if (ret < 0) {
         return ret;
     }

     *result = be64_to_cpu(buffer);
     return 0;
 }

 static int read_uint32(BlockDriverState *bs, int64_t offset, uint32_t *result)
 {
     uint32_t buffer;
     int ret;

     ret = bdrv_pread(bs->file, offset, &buffer, 4);
     if (ret < 0) {
         return ret;
     }

     *result = be32_to_cpu(buffer);
     return 0;
 }

 /* Increase max chunk sizes, if necessary.  This function is used to calculate
  * the buffer sizes needed for compressed/uncompressed chunk I/O.
  */
 static void update_max_chunk_size(BDRVDMGState *s, uint32_t chunk,
                                   uint32_t *max_compressed_size,
                                   uint32_t *max_sectors_per_chunk)
 {
     uint32_t compressed_size = 0;
     uint32_t uncompressed_sectors = 0;

     switch (s->types[chunk]) {
     case 0x80000005: /* zlib compressed */
         compressed_size = s->lengths[chunk];
         uncompressed_sectors = s->sectorcounts[chunk];
         break;
     case 1: /* copy */
         uncompressed_sectors = (s->lengths[chunk] + 511) / 512;
         break;
     case 2: /* zero */
         uncompressed_sectors = s->sectorcounts[chunk];
         break;
     }

     if (compressed_size > *max_compressed_size) {
         *max_compressed_size = compressed_size;
     }
     if (uncompressed_sectors > *max_sectors_per_chunk) {
         *max_sectors_per_chunk = uncompressed_sectors;
     }
 }

 static int dmg_open(BlockDriverState *bs, QDict *options, int flags,
                     Error **errp)
 {
     BDRVDMGState *s = bs->opaque;
     uint64_t info_begin, info_end, last_in_offset, last_out_offset;
     uint32_t count, tmp;
     uint32_t max_compressed_size = 1, max_sectors_per_chunk = 1, i;
     int64_t offset;
     int ret;

     bs->read_only = 1;
     s->n_chunks = 0;
     s->offsets = s->lengths = s->sectors = s->sectorcounts = NULL;

     /* read offset of info blocks */
     offset = bdrv_getlength(bs->file);
     if (offset < 0) {
         ret = offset;
         goto fail;
     }
     offset -= 0x1d8;

     ret = read_uint64(bs, offset, &info_begin);
     if (ret < 0) {
         goto fail;
     } else if (info_begin == 0) {
         ret = -EINVAL;
         goto fail;
     }

     ret = read_uint32(bs, info_begin, &tmp);
     if (ret < 0) {
         goto fail;
     } else if (tmp != 0x100) {
         ret = -EINVAL;
         goto fail;
     }

     ret = read_uint32(bs, info_begin + 4, &count);
     if (ret < 0) {
         goto fail;
     } else if (count == 0) {
         ret = -EINVAL;
         goto fail;
     }
     info_end = info_begin + count;

     offset = info_begin + 0x100;

     /* read offsets */
     last_in_offset = last_out_offset = 0;
     while (offset < info_end) {
         uint32_t type;

         ret = read_uint32(bs, offset, &count);
         if (ret < 0) {
             goto fail;
         } else if (count == 0) {
             ret = -EINVAL;
             goto fail;
         }
         offset += 4;

         ret = read_uint32(bs, offset, &type);
         if (ret < 0) {
             goto fail;
         }

         if (type == 0x6d697368 && count >= 244) {
             size_t new_size;
             uint32_t chunk_count;

             offset += 4;
             offset += 200;

             chunk_count = (count - 204) / 40;
             new_size = sizeof(uint64_t) * (s->n_chunks + chunk_count);
             s->types = g_realloc(s->types, new_size / 2);
             s->offsets = g_realloc(s->offsets, new_size);
             s->lengths = g_realloc(s->lengths, new_size);
             s->sectors = g_realloc(s->sectors, new_size);
             s->sectorcounts = g_realloc(s->sectorcounts, new_size);

             for (i = s->n_chunks; i < s->n_chunks + chunk_count; i++) {
                 ret = read_uint32(bs, offset, &s->types[i]);
                 if (ret < 0) {
                     goto fail;
                 }
                 offset += 4;
                 if (s->types[i] != 0x80000005 && s->types[i] != 1 &&
                     s->types[i] != 2) {
                     if (s->types[i] == 0xffffffff && i > 0) {
                         last_in_offset = s->offsets[i - 1] + s->lengths[i - 1];
                         last_out_offset = s->sectors[i - 1] +
                                           s->sectorcounts[i - 1];
                     }
                     chunk_count--;
                     i--;
                     offset += 36;
                     continue;
                 }
                 offset += 4;

                 ret = read_uint64(bs, offset, &s->sectors[i]);
                 if (ret < 0) {
                     goto fail;
                 }
                 s->sectors[i] += last_out_offset;
                 offset += 8;

                 ret = read_uint64(bs, offset, &s->sectorcounts[i]);
                 if (ret < 0) {
                     goto fail;
                 }
                 offset += 8;

                 if (s->sectorcounts[i] > DMG_SECTORCOUNTS_MAX) {
                     error_report("sector count %" PRIu64 " for chunk %u is "
                                  "larger than max (%u)",
                                  s->sectorcounts[i], i, DMG_SECTORCOUNTS_MAX);
                     ret = -EINVAL;
                     goto fail;
                 }

                 ret = read_uint64(bs, offset, &s->offsets[i]);
                 if (ret < 0) {
                     goto fail;
                 }
                 s->offsets[i] += last_in_offset;
                 offset += 8;

                 ret = read_uint64(bs, offset, &s->lengths[i]);
                 if (ret < 0) {
                     goto fail;
                 }
                 offset += 8;

                 if (s->lengths[i] > DMG_LENGTHS_MAX) {
                     error_report("length %" PRIu64 " for chunk %u is larger "
                                  "than max (%u)",
                                  s->lengths[i], i, DMG_LENGTHS_MAX);
                     ret = -EINVAL;
                     goto fail;
                 }

                 update_max_chunk_size(s, i, &max_compressed_size,
                                       &max_sectors_per_chunk);
             }
             s->n_chunks += chunk_count;
         }
     }

     /* initialize zlib engine */
     s->compressed_chunk = g_malloc(max_compressed_size + 1);
     s->uncompressed_chunk = g_malloc(512 * max_sectors_per_chunk);
     if (inflateInit(&s->zstream) != Z_OK) {
         ret = -EINVAL;
         goto fail;
     }

     s->current_chunk = s->n_chunks;

     qemu_co_mutex_init(&s->lock);
     return 0;

 fail:
     g_free(s->types);
     g_free(s->offsets);
     g_free(s->lengths);
     g_free(s->sectors);
     g_free(s->sectorcounts);
     g_free(s->compressed_chunk);
     g_free(s->uncompressed_chunk);
     return ret;
 }

 static inline int is_sector_in_chunk(BDRVDMGState* s,
                 uint32_t chunk_num, uint64_t sector_num)
 {
     if (chunk_num >= s->n_chunks || s->sectors[chunk_num] > sector_num ||
             s->sectors[chunk_num] + s->sectorcounts[chunk_num] <= sector_num) {
         return 0;
     } else {
         return -1;
     }
 }

 static inline uint32_t search_chunk(BDRVDMGState *s, uint64_t sector_num)
 {
     /* binary search */
     uint32_t chunk1 = 0, chunk2 = s->n_chunks, chunk3;
     while (chunk1 != chunk2) {
         chunk3 = (chunk1 + chunk2) / 2;
         if (s->sectors[chunk3] > sector_num) {
             chunk2 = chunk3;
         } else if (s->sectors[chunk3] + s->sectorcounts[chunk3] > sector_num) {
             return chunk3;
         } else {
             chunk1 = chunk3;
         }
     }
     return s->n_chunks; /* error */
 }

 static inline int dmg_read_chunk(BlockDriverState *bs, uint64_t sector_num)
 {
     BDRVDMGState *s = bs->opaque;

     if (!is_sector_in_chunk(s, s->current_chunk, sector_num)) {
         int ret;
         uint32_t chunk = search_chunk(s, sector_num);

         if (chunk >= s->n_chunks) {
             return -1;
         }

         s->current_chunk = s->n_chunks;
         switch (s->types[chunk]) {
         case 0x80000005: { /* zlib compressed */
             /* we need to buffer, because only the chunk as whole can be
              * inflated. */
             ret = bdrv_pread(bs->file, s->offsets[chunk],
                              s->compressed_chunk, s->lengths[chunk]);
             if (ret != s->lengths[chunk]) {
                 return -1;
             }

             s->zstream.next_in = s->compressed_chunk;
             s->zstream.avail_in = s->lengths[chunk];
             s->zstream.next_out = s->uncompressed_chunk;
             s->zstream.avail_out = 512 * s->sectorcounts[chunk];
             ret = inflateReset(&s->zstream);
             if (ret != Z_OK) {
                 return -1;
             }
             ret = inflate(&s->zstream, Z_FINISH);
             if (ret != Z_STREAM_END ||
                 s->zstream.total_out != 512 * s->sectorcounts[chunk]) {
                 return -1;
             }
             break; }
         case 1: /* copy */
             ret = bdrv_pread(bs->file, s->offsets[chunk],
                              s->uncompressed_chunk, s->lengths[chunk]);
             if (ret != s->lengths[chunk]) {
                 return -1;
             }
             break;
         case 2: /* zero */
             memset(s->uncompressed_chunk, 0, 512 * s->sectorcounts[chunk]);
             break;
         }
         s->current_chunk = chunk;
     }
     return 0;
 }

 static int dmg_read(BlockDriverState *bs, int64_t sector_num,
                     uint8_t *buf, int nb_sectors)
 {
     BDRVDMGState *s = bs->opaque;
     int i;

     for (i = 0; i < nb_sectors; i++) {
         uint32_t sector_offset_in_chunk;
         if (dmg_read_chunk(bs, sector_num + i) != 0) {
             return -1;
         }
         sector_offset_in_chunk = sector_num + i - s->sectors[s->current_chunk];
         memcpy(buf + i * 512,
                s->uncompressed_chunk + sector_offset_in_chunk * 512, 512);
     }
     return 0;
 }

 static coroutine_fn int dmg_co_read(BlockDriverState *bs, int64_t sector_num,
                                     uint8_t *buf, int nb_sectors)
 {
     int ret;
     BDRVDMGState *s = bs->opaque;
     qemu_co_mutex_lock(&s->lock);
     ret = dmg_read(bs, sector_num, buf, nb_sectors);
     qemu_co_mutex_unlock(&s->lock);
     return ret;
 }

 static void dmg_close(BlockDriverState *bs)
 {
     BDRVDMGState *s = bs->opaque;

     g_free(s->types);
     g_free(s->offsets);
     g_free(s->lengths);
     g_free(s->sectors);
     g_free(s->sectorcounts);
     g_free(s->compressed_chunk);
     g_free(s->uncompressed_chunk);

     inflateEnd(&s->zstream);
 }

 static BlockDriver bdrv_dmg = {
     .format_name    = "dmg",
     .instance_size  = sizeof(BDRVDMGState),
     .bdrv_probe     = dmg_probe,
     .bdrv_open      = dmg_open,
     .bdrv_read      = dmg_co_read,
     .bdrv_close     = dmg_close,
 };

 static void bdrv_dmg_init(void)
 {
     bdrv_register(&bdrv_dmg);
 }

 block_init(bdrv_dmg_init);
	/*
	* QEMU Block driver for DMG images
	*
	* Copyright (c) 2004 Johannes E. Schindelin
	*
	* Permission is hereby granted, free of charge, to any person obtaining a copy
	* of this software and associated documentation files (the "Software"), to deal
	* in the Software without restriction, including without limitation the rights
	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	* copies of the Software, and to permit persons to whom the Software is
	* furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice shall be included in
	* all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	* THE SOFTWARE.
	*/
	#include "qemu-common.h"
	#include "block/block_int.h"
	#include "qemu/bswap.h"
	#include "qemu/module.h"
	#include <zlib.h>

	enum {
	/* Limit chunk sizes to prevent unreasonable amounts of memory being used
	* or truncating when converting to 32-bit types
	*/
	DMG_LENGTHS_MAX = 64 * 1024 * 1024, /* 64 MB */
	DMG_SECTORCOUNTS_MAX = DMG_LENGTHS_MAX / 512,
	};

	typedef struct BDRVDMGState {
	CoMutex lock;
	/* each chunk contains a certain number of sectors,
	* offsets[i] is the offset in the .dmg file,
	* lengths[i] is the length of the compressed chunk,
	* sectors[i] is the sector beginning at offsets[i],
	* sectorcounts[i] is the number of sectors in that chunk,
	* the sectors array is ordered
	* 0<=i<n_chunks */

	uint32_t n_chunks;
	uint32_t* types;
	uint64_t* offsets;
	uint64_t* lengths;
	uint64_t* sectors;
	uint64_t* sectorcounts;
	uint32_t current_chunk;
	uint8_t *compressed_chunk;
	uint8_t *uncompressed_chunk;
	z_stream zstream;
	} BDRVDMGState;

	static int dmg_probe(const uint8_t buf, int buf_size, const char filename)
	{
	int len;

	if (!filename) {
	return 0;
	}

	len = strlen(filename);
	if (len > 4 && !strcmp(filename + len - 4, ".dmg")) {
	return 2;
	}
	return 0;
	}

	static int read_uint64(BlockDriverState bs, int64_t offset, uint64_t result)
	{
	uint64_t buffer;
	int ret;

	ret = bdrv_pread(bs->file, offset, &buffer, 8);
	if (ret < 0) {
	return ret;
	}

	*result = be64_to_cpu(buffer);
	return 0;
	}

	static int read_uint32(BlockDriverState bs, int64_t offset, uint32_t result)
	{
	uint32_t buffer;
	int ret;

	ret = bdrv_pread(bs->file, offset, &buffer, 4);
	if (ret < 0) {
	return ret;
	}

	*result = be32_to_cpu(buffer);
	return 0;
	}

	/* Increase max chunk sizes, if necessary. This function is used to calculate
	* the buffer sizes needed for compressed/uncompressed chunk I/O.
	*/
	static void update_max_chunk_size(BDRVDMGState *s, uint32_t chunk,
	uint32_t *max_compressed_size,
	uint32_t *max_sectors_per_chunk)
	{
	uint32_t compressed_size = 0;
	uint32_t uncompressed_sectors = 0;

	switch (s->types[chunk]) {
	case 0x80000005: /* zlib compressed */
	compressed_size = s->lengths[chunk];
	uncompressed_sectors = s->sectorcounts[chunk];
	break;
	case 1: /* copy */
	uncompressed_sectors = (s->lengths[chunk] + 511) / 512;
	break;
	case 2: /* zero */
	uncompressed_sectors = s->sectorcounts[chunk];
	break;
	}

	if (compressed_size > *max_compressed_size) {
	*max_compressed_size = compressed_size;
	}
	if (uncompressed_sectors > *max_sectors_per_chunk) {
	*max_sectors_per_chunk = uncompressed_sectors;
	}
	}

	static int dmg_open(BlockDriverState bs, QDict options, int flags,
	Error **errp)
	{
	BDRVDMGState *s = bs->opaque;
	uint64_t info_begin, info_end, last_in_offset, last_out_offset;
	uint32_t count, tmp;
	uint32_t max_compressed_size = 1, max_sectors_per_chunk = 1, i;
	int64_t offset;
	int ret;

	bs->read_only = 1;
	s->n_chunks = 0;
	s->offsets = s->lengths = s->sectors = s->sectorcounts = NULL;

	/* read offset of info blocks */
	offset = bdrv_getlength(bs->file);
	if (offset < 0) {
	ret = offset;
	goto fail;
	}
	offset -= 0x1d8;

	ret = read_uint64(bs, offset, &info_begin);
	if (ret < 0) {
	goto fail;
	} else if (info_begin == 0) {
	ret = -EINVAL;
	goto fail;
	}

	ret = read_uint32(bs, info_begin, &tmp);
	if (ret < 0) {
	goto fail;
	} else if (tmp != 0x100) {
	ret = -EINVAL;
	goto fail;
	}

	ret = read_uint32(bs, info_begin + 4, &count);
	if (ret < 0) {
	goto fail;
	} else if (count == 0) {
	ret = -EINVAL;
	goto fail;
	}
	info_end = info_begin + count;

	offset = info_begin + 0x100;

	/* read offsets */
	last_in_offset = last_out_offset = 0;
	while (offset < info_end) {
	uint32_t type;

	ret = read_uint32(bs, offset, &count);
	if (ret < 0) {
	goto fail;
	} else if (count == 0) {
	ret = -EINVAL;
	goto fail;
	}
	offset += 4;

	ret = read_uint32(bs, offset, &type);
	if (ret < 0) {
	goto fail;
	}

	if (type == 0x6d697368 && count >= 244) {
	size_t new_size;
	uint32_t chunk_count;

	offset += 4;
	offset += 200;

	chunk_count = (count - 204) / 40;
	new_size = sizeof(uint64_t) * (s->n_chunks + chunk_count);
	s->types = g_realloc(s->types, new_size / 2);
	s->offsets = g_realloc(s->offsets, new_size);
	s->lengths = g_realloc(s->lengths, new_size);
	s->sectors = g_realloc(s->sectors, new_size);
	s->sectorcounts = g_realloc(s->sectorcounts, new_size);

	for (i = s->n_chunks; i < s->n_chunks + chunk_count; i++) {
	ret = read_uint32(bs, offset, &s->types[i]);
	if (ret < 0) {
	goto fail;
	}
	offset += 4;
	if (s->types[i] != 0x80000005 && s->types[i] != 1 &&
	s->types[i] != 2) {
	if (s->types[i] == 0xffffffff && i > 0) {
	last_in_offset = s->offsets[i - 1] + s->lengths[i - 1];
	last_out_offset = s->sectors[i - 1] +
	s->sectorcounts[i - 1];
	}
	chunk_count--;
	i--;
	offset += 36;
	continue;
	}
	offset += 4;

	ret = read_uint64(bs, offset, &s->sectors[i]);
	if (ret < 0) {
	goto fail;
	}
	s->sectors[i] += last_out_offset;
	offset += 8;

	ret = read_uint64(bs, offset, &s->sectorcounts[i]);
	if (ret < 0) {
	goto fail;
	}
	offset += 8;

	if (s->sectorcounts[i] > DMG_SECTORCOUNTS_MAX) {
	error_report("sector count %" PRIu64 " for chunk %u is "
	"larger than max (%u)",
	s->sectorcounts[i], i, DMG_SECTORCOUNTS_MAX);
	ret = -EINVAL;
	goto fail;
	}

	ret = read_uint64(bs, offset, &s->offsets[i]);
	if (ret < 0) {
	goto fail;
	}
	s->offsets[i] += last_in_offset;
	offset += 8;

	ret = read_uint64(bs, offset, &s->lengths[i]);
	if (ret < 0) {
	goto fail;
	}
	offset += 8;

	if (s->lengths[i] > DMG_LENGTHS_MAX) {
	error_report("length %" PRIu64 " for chunk %u is larger "
	"than max (%u)",
	s->lengths[i], i, DMG_LENGTHS_MAX);
	ret = -EINVAL;
	goto fail;
	}

	update_max_chunk_size(s, i, &max_compressed_size,
	&max_sectors_per_chunk);
	}
	s->n_chunks += chunk_count;
	}
	}

	/* initialize zlib engine */
	s->compressed_chunk = g_malloc(max_compressed_size + 1);
	s->uncompressed_chunk = g_malloc(512 * max_sectors_per_chunk);
	if (inflateInit(&s->zstream) != Z_OK) {
	ret = -EINVAL;
	goto fail;
	}

	s->current_chunk = s->n_chunks;

	qemu_co_mutex_init(&s->lock);
	return 0;

	fail:
	g_free(s->types);
	g_free(s->offsets);
	g_free(s->lengths);
	g_free(s->sectors);
	g_free(s->sectorcounts);
	g_free(s->compressed_chunk);
	g_free(s->uncompressed_chunk);
	return ret;
	}

	static inline int is_sector_in_chunk(BDRVDMGState* s,
	uint32_t chunk_num, uint64_t sector_num)
	{
	if (chunk_num >= s->n_chunks \|\| s->sectors[chunk_num] > sector_num \|\|
	s->sectors[chunk_num] + s->sectorcounts[chunk_num] <= sector_num) {
	return 0;
	} else {
	return -1;
	}
	}

	static inline uint32_t search_chunk(BDRVDMGState *s, uint64_t sector_num)
	{
	/* binary search */
	uint32_t chunk1 = 0, chunk2 = s->n_chunks, chunk3;
	while (chunk1 != chunk2) {
	chunk3 = (chunk1 + chunk2) / 2;
	if (s->sectors[chunk3] > sector_num) {
	chunk2 = chunk3;
	} else if (s->sectors[chunk3] + s->sectorcounts[chunk3] > sector_num) {
	return chunk3;
	} else {
	chunk1 = chunk3;
	}
	}
	return s->n_chunks; /* error */
	}

	static inline int dmg_read_chunk(BlockDriverState *bs, uint64_t sector_num)
	{
	BDRVDMGState *s = bs->opaque;

	if (!is_sector_in_chunk(s, s->current_chunk, sector_num)) {
	int ret;
	uint32_t chunk = search_chunk(s, sector_num);

	if (chunk >= s->n_chunks) {
	return -1;
	}

	s->current_chunk = s->n_chunks;
	switch (s->types[chunk]) {
	case 0x80000005: { /* zlib compressed */
	/* we need to buffer, because only the chunk as whole can be
	* inflated. */
	ret = bdrv_pread(bs->file, s->offsets[chunk],
	s->compressed_chunk, s->lengths[chunk]);
	if (ret != s->lengths[chunk]) {
	return -1;
	}

	s->zstream.next_in = s->compressed_chunk;
	s->zstream.avail_in = s->lengths[chunk];
	s->zstream.next_out = s->uncompressed_chunk;
	s->zstream.avail_out = 512 * s->sectorcounts[chunk];
	ret = inflateReset(&s->zstream);
	if (ret != Z_OK) {
	return -1;
	}
	ret = inflate(&s->zstream, Z_FINISH);
	if (ret != Z_STREAM_END \|\|
	s->zstream.total_out != 512 * s->sectorcounts[chunk]) {
	return -1;
	}
	break; }
	case 1: /* copy */
	ret = bdrv_pread(bs->file, s->offsets[chunk],
	s->uncompressed_chunk, s->lengths[chunk]);
	if (ret != s->lengths[chunk]) {
	return -1;
	}
	break;
	case 2: /* zero */
	memset(s->uncompressed_chunk, 0, 512 * s->sectorcounts[chunk]);
	break;
	}
	s->current_chunk = chunk;
	}
	return 0;
	}

	static int dmg_read(BlockDriverState *bs, int64_t sector_num,
	uint8_t *buf, int nb_sectors)
	{
	BDRVDMGState *s = bs->opaque;
	int i;

	for (i = 0; i < nb_sectors; i++) {
	uint32_t sector_offset_in_chunk;
	if (dmg_read_chunk(bs, sector_num + i) != 0) {
	return -1;
	}
	sector_offset_in_chunk = sector_num + i - s->sectors[s->current_chunk];
	memcpy(buf + i * 512,
	s->uncompressed_chunk + sector_offset_in_chunk * 512, 512);
	}
	return 0;
	}

	static coroutine_fn int dmg_co_read(BlockDriverState *bs, int64_t sector_num,
	uint8_t *buf, int nb_sectors)
	{
	int ret;
	BDRVDMGState *s = bs->opaque;
	qemu_co_mutex_lock(&s->lock);
	ret = dmg_read(bs, sector_num, buf, nb_sectors);
	qemu_co_mutex_unlock(&s->lock);
	return ret;
	}

	static void dmg_close(BlockDriverState *bs)
	{
	BDRVDMGState *s = bs->opaque;

	g_free(s->types);
	g_free(s->offsets);
	g_free(s->lengths);
	g_free(s->sectors);
	g_free(s->sectorcounts);
	g_free(s->compressed_chunk);
	g_free(s->uncompressed_chunk);

	inflateEnd(&s->zstream);
	}

	static BlockDriver bdrv_dmg = {
	.format_name = "dmg",
	.instance_size = sizeof(BDRVDMGState),
	.bdrv_probe = dmg_probe,
	.bdrv_open = dmg_open,
	.bdrv_read = dmg_co_read,
	.bdrv_close = dmg_close,
	};

	static void bdrv_dmg_init(void)
	{
	bdrv_register(&bdrv_dmg);
	}

	block_init(bdrv_dmg_init);